Abstract
The method of drilling and blasting with explosives is widely used in rock fragmentation applications in underground construction projects, such as tunnels and caverns. However, the use of explosives is associated with rigorous safety and environmental constraints, since blasting creates toxic fumes, ground vibrations, and dust. Because of these constraints, there has been a growing interest in transitioning away from explosives-based rock fragmentation. The use of explosives-free methods could lead to continuous operation by eliminating the need for idle time with additional ventilation required to exhaust the blast fumes. This paper first presents a critical review of various methods that have been developed so far for rock fragmentation without explosives. Such methods include thermal fragmentation, plasma blasting, controlled foam injection, radial-axial splitter, and supercritical carbon dioxide. Thermal fragmentation, as the name implies, uses high heat to spall high-grade ore. However, it requires high heat energy, which requires additional ventilation as compared to normal conditions to cool the work area. Plasma blasting uses a high temperature and pressure plasma to fracture rock in a safe manner. While this method may be environmentally friendly, its usage may significantly slow tunnel development due to the need to haul one or more large energy capacitor banks into and out of the work area repeatedly. Controlled foam injection is another chemical method, whereby foam is the medium for fracturing. Although claimed to be environmentally friendly, it may still pose safety risks such as air blast or flyrock due to its dynamic nature. A radial-axial splitter (RASP) is an instrument specially designed to fracture a borehole in the rock face but only at the pace of one hole at a time. Supercritical carbon dioxide is used with the equipment designed to provide a high-pressure jet stream to fracture rock, and replaces water in these instruments. The method of soundless chemical demolition agents (SCDA) is evaluated in more detail and its merits over others are highlighted, making it a potentially viable alternative to blasting with explosives in underground excavation applications. Future work involves the optimization of SCDA for implementation in underground mines. The discussion compares the key features and limitations, and future work needs are underlined.
Highlights
IntroductionWhile drill-and-blast is the most conventional method for rock fragmentation in mine development and ore production, mechanical excavation is commonly used, especially in soft rock formations
Licensee MDPI, Basel, Switzerland.Rock excavation methods can be classified into three categories: drill and blast (DB), mechanical excavation, and specialized explosive-free approaches
This paper describes six selected explosives-free methods for rock breakage, notably thermal fragmentation, plasma blasting technology, controlled foam injection, radial-axial splitter, supercritical carbon dioxide, and soundless chemical demolition agents (SCDA)
Summary
While drill-and-blast is the most conventional method for rock fragmentation in mine development and ore production, mechanical excavation is commonly used, especially in soft rock formations This category comprises the use of a tunnel boring machine (TBM), which can be adopted for tunnel driving in hard rock. While drill-and-blast and mechanical methods are the two main categories for rock excavation techniques, an increasing amount of interest has been drawn in recent years towards the use of explosives-free specialized methods The development of such methods offers the advantage of eliminating the disruption to tunneling activities—step 3 in Figure 1—and avoids blast fumes, dust, and noise, while potentially reducing damage to wall rock and achieving a better fragment size distribution. A review of recent methods for rock breakage without explosives is presented, briefly explaining the fundamental concepts behind each method, and highlighting its limitations and features
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